The present invention relates to a high-purity copper-manganese-alloy that has a self-diffusion suppression function useful and suitable for forming semiconductor copper alloy wiring and can effectively prevent contamination of the periphery of the wiring due to diffusion of active copper. In particular, the invention relates to a high-purity copper-manganese-alloy sputtering target that can form a thin film having excellent uniformity.
Conventionally, Al alloys (specific resistance: about 3.0 μΩ·cm) were used as a wiring material of semiconductor elements. However, copper wiring having a lower resistance (specific resistance: about 2.0 μΩ·cm) has been put into practical use with miniaturization of wiring. Copper wiring is generally formed by forming a diffusion barrier layer of, for example, Ta or TaN in wiring or wiring grooves and then forming a film of copper by sputtering. Generally, copper having a high purity of 5N to 6 N is produced from electrolytic copper having a purity of about 4 N (excluding gas components) as a crude metal by a wet or dry purification process, and the purified copper is used as a sputtering target.
As described above, copper is very effective for semiconductor wiring. However, copper itself is a very active metal and easily diffuses, and therefore causes a problem of contaminating a Si substrate or its periphery through the semiconductor Si substrate or the insulating film thereon. In particular, with progress in miniaturization of wiring, the problem cannot be sufficiently prevented by the conventional diffusion barrier layer of Ta or TaN only, and copper wiring materials themselves are also required to be improved. Accordingly, as a copper wiring material, a Cu—Mn alloy, which is a copper alloy prepared by adding manganese (Mn) to copper (Cu), having a self-diffusion suppression function by forming a barrier layer by itself through a reaction of Mn in the alloy with oxygen in an insulating film has been proposed.
The semiconductor copper alloy wiring is formed using a copper-manganese alloy sputtering target. In such semiconductor copper alloy wiring, the in-plane variation in thickness or sheet resistance of the wiring layer, which has not conventionally caused any problem, causes a problem of reducing the yield of chips product) prepared from a wafer, with progresses of miniaturization, density growth, and integration of semiconductor devices and with progresses of miniaturization and increase in number of wiring layers. Accordingly, there is a demand for a copper-manganese alloy sputtering target that can form a thin film (wiring) with less variation.
The followings are examples of the Cu—Mn alloy sputtering target:
Patent Literature 1 describes a sputtering target composed of 0.1 to 20.0 at % of Mn, 0.05 at % or less of inevitable impurity elements having diffusion coefficients lower than the self-diffusion coefficient of Cu, and the remainder being Cu;
Patent Literature 2 describes a sputtering target composed of 0.1 to 1.0 at % of B as an additive element, 0.1 to 2.0 at % of Mn and/or Ni, and the remainder being Cu and inevitable impurities;
Patent Literature 3 describes a sputtering target composed of 0.1 to 1.0 at % of B as an additive element, 0.1 to 2.0 at % of an element (including Mn) that forms a compound with B, and the remainder being Cu and inevitable impurities;
Patent Literature 4 describes a sputtering target composed of at least one component selected from the group consisting of V, Nb, Fe, Co, Ni, Zn, and Mg and at least one component selected from the group consisting of Sc, Al, Y, and Cr in a total amount of 0.005 to 0.5% by mass, 0.1 to 5 ppm of oxygen, and the remainder being Cu and inevitable impurities;
Patent Literature 5 describes a sputtering target composed of oxygen in an amount higher than 6% by mole and 20% by mole or less, at least one selected from Mo, Mn, Ca, Zn, Ni, Ti, Al, Mg, and Fe in a total of 0.2 to 5% by mole, and the remainder being Cu and inevitable impurities;
Patent Literature 6 describes a sintered sputtering target material composed of a metal powder of Mn, B, Bi, or Ge and an alloy powder or sintered metal containing X (including Cu) and Y, in which the amount of crystal grains having an average particle diameter of 0.1 to 300 μm is 50% or more, and the amount of gas included is 600 ppm or less; and
Patent Literature 7 describes a sputtering target composed of 0.6 to 30% by mass of Mn for suppressing occurrence of particles, 40 ppm or less of metal based impurities, 10 ppm or less of oxygen, 5 ppm or less of nitrogen, 5 ppm or less of hydrogen, 10 ppm or less of carbon, and the remainder being Cu.
In these sputtering targets, however, the in-plane variation of the copper-manganese alloy thin film formed on a wafer is not necessarily low.
Furthermore, the present applicant has proposed a semiconductor element wiring material, which is a sputtering target for forming semiconductor copper alloy wiring and composed of Mn in an amount of 0.05 to 5 wt %, at least one element selected from Sb, Zr, Ti, Cr, Ag, Au, Cd, In, and As in a total amount of 10 wt ppm or less, and the remainder being Cu (see Patent Literature 8).
This is effective for enhancing the self-diffusion suppression function, but the purpose thereof is not a reduction in in-plane variation of the copper-manganese alloy thin film formed on a wafer.
The present applicant has disclosed a semiconductor copper alloy wiring material composed of a Cu—Mn alloy (see Patent Literature 9), in particular, has proposed a sputtering target composed of 0.05 to 20 wt % of Mn, a total amount of 500 wt ppm or less of Be, B, Mg, Al, Si, Ca, Ba, La, and Ce, and the remainder being Cu and inevitable impurities.
This is also effective for enhancing the self-diffusion suppression function, but the purpose thereof is not a reduction in in-plane variation of the copper-manganese alloy thin film formed on a wafer.    Patent Literature 1: Japanese Patent No. 4065959    Patent Literature 2: Japanese Patent Laid-Open No. 2009-97085    Patent Literature 3: Japanese Patent Laid-Open No. 2010-248619    Patent Literature 4: Japanese Patent Laid-Open No. 2002-294437    Patent Literature 5: Japanese Patent Laid-Open No. 2008-311283    Patent Literature 6: Japanese Patent Laid-Open No. 2009-74127    Patent Literature 7: Japanese Patent Laid-Open No. 2007-51351    Patent Literature 8: Japanese Patent Laid-Open No. 2006-73863    Patent Literature 9: International Publication No. WO2008/041535